1. Field of the Invention
This invention relates to an electrophoresis device for separating and analyzing high molecular materials, such as proteins and nucleic acids which can have an electric charge in a solution, based on differences in their molecular charges and in their molecular weights.
2. Description of the Prior Art
The electrophoresis technique has been widely known for separating and analyzing proteins, nucleic acids, their degradation products and the like based on differences in molecular charges and in molecular weights in a membrane-like medium such as gel membrane and filter paper containing a buffer.
In particular, technique for determining base sequences of radioactive-labeled nucleic acids by using autoradiography is important in the field of genetic technology. In the electrophoresis for this purpose, a base-specific reaction product (mixture) of a radioactive-labeled DNA or of a fragment of such a DNA is subjected to electrophoresis along the direction of electric field of electrophoresis medium. In general, a plurality of base-specific reaction products are migrated in parallel along the direction of electric field. After this electrophoresis, a plurality of rows of electrophoresis patterns are obtained as an autoradiographic image (autoradiogram). Then, base sequence determination is conducted by comparing and contrasting these patterns therebetween.
Heretofore, an experimenter of electrophoresis has had to prepare by himself a gel membrane consisting of starch, polyacrylamide, etc. on a flat substrate such as a glass plate on every occasion for electrophoresis. This work is quite troublesome and has been a heavy burden to the experimenter who uses electrophoresis. Recently, in order to reduce this burden, a sheet device prefabricated for electrophoresis has become commercially available in which two electrically-insulated, flexible, water-impervious sheets (support sheet and cover sheet) are disposed face to face sandwiching therebetween a spacer of a predetermined thickness at each end in the width direction thereof, and a gel membrane is contained within thus formed space as electrophoresis medium.
When such a device is used for electrophoresis, it is necessary to pour the sample liquid, which is to be subjected to electrophoresis, into the upper end of gel membrane (i.e. the end that is positioned at the upper portion of an upright electrophoresis apparatus and does not face the above-mentioned spacer) before beginning the electrophoresis. Accordingly, forming of a plurality of rectangular wells (or slots) each provided with an open end has widely been used in practice. This method, however, results in a gap of l mm or more formed between a pair of adjacent electrophoresis areas (lanes), corresponding to the interval between the adjacent wells. In the base sequence determination of a DNA, where electrophoretic images of fragments containing four kinds of bases (A, G, C, T), respectively, have to be compared and collated each other, such a gap between the lanes of electrophoresis images makes the collation difficult. It is therefore desirable that there is no or little distance between the electrophoresis lanes.
In order to fulfill this requirement, it has been known to dispose a so-called shark's teeth comb, which is a flat plate-like member having saw-like protrusions, such that it is in close contact with or partially intruded into an end of a gel membrane, and to pour a sample liquid into a substantially triangular space formed by the end of the gel membrane and a pair of adjacent end faces of the protrusions. If the thickness of the comb is equal to that of the gel membrane in this case, the sample liquid will often invade a neighboring lane across a partition of the comb after pouring the liquid before beginning electrophoresis. This phenomenon is likely to occur particularly when a sample liquid is poured into a lane after electrophoresis has been carried out using the adjacent lane for a few hours. In an extreme case, the comb may slip off from the position where it was fixed so that pouring of the sample liquid is impossible.